The only problem I see with practicing with the .22 is that it does not punish improper technique. Therefore, any flaws with positioning will go unnoticed until you go back to the big gun.

Try this, get a snap cap that can be cycled through. Have someone help you by placing the snap cap in between the real rounds without you knowing where it is. Keep doing this until you don't flinch at all when you pull the trigger onthe "dummy" round.

If that's not possible for you, just practice, practice, practice. You'll get used to the noise and recoil. After you've fired enough rounds without trying to anticipate the shot, you'll stop flinching.